Trees and bushes with a special characteristic grow in international phenological gardens. All are clonal descendants of a single mother plant enabling uniform comparison and study of the impact of climate factors on the phenological development of plants in a wider geographical area. The International Phenological Gardens in Europe network includes already 89 gardens and encompasses a wide geographical area from Ireland and Finland in the north, to Portugal in the west, Macedonia in the south and the Baltic countries in the east. The phenological monitoring data is transmitted into the data archive of the International Phenological Gardens in Europe at the Humboldt University in Berlin. The phenological monitoring data is a priceless source for the research of the impact of climate change on the plant world. The International Phenological Park in Tivoli is the only park of its kind in Slovenia.